Method for producing conductive polyaniline

ABSTRACT

A method for producing a conductive polyaniline comprising oxidative polymerizing aniline or its derivative in the presence of at least one member of a sulfonic acid compound and a water-insoluble organic polymer compound having protonic acid group in a mixed layer composed of an aqueous layer and organic layer, during which it establishes the presence of a molecular weight adjusting agent and, optionally, a phase transfer catalyst so as to stably disperse them in an organic solvent, and an organic polymer composition containing the conductive polyaniline.

This application is a continuation-in-part application of InternationalApplication No. PCT/JP2004/015203, designating the United States ofAmerica originally filed in Japan on Oct. 7, 2004.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method for producing a conductivepolyaniline and an organic polymer composition containing the same. Moreparticularly, it relates to a method for producing a conductivepolyaniline stably dispersed in an organic solvent and having a highelectroconductivity and an organic polymer composition containing thesame. The present invention also relates to a conductive substrateformed from a dispersion of the above conductive polyaniline having ahigh electroconductivity and stably dispersed in an organic solvent aswell as a photovoltaic device and dye-sensitized solar cell using thesame.

2. Description of the Related Art

It is known to obtain a conductive polymer including electrolyte ions asa dopant by chemical oxidative polymerization of aniline or an anilinederivative. However, conductive polyaniline is generally insoluble in anorganic solvent and also is non-meltable, and therefore, is poor inprocessability and difficult to develop applications thereof. Further,it has been reported to obtain polyaniline and polyaniline derivativessoluble in an organic solvent by polymerization of a salt of an anilinecomprising sulfonic acid such as dodecylbenzene sulfonic acid,dinonylnaphthalene sulfonic acid and aniline or its derivative (JapaneseUnexamined Patent Publication (Kokai) No. 6-279584 No. 2003-176409, U.S.Pat. No. 5,232,631). However, the solubility of polyaniline or apolyaniline derivative in an organic solvent is not necessarily high.For example, the solubility of aniline dodecylbenzene sulfonate intoluene or xylene is at most 0.5%. Thus, a method for producingpolyaniline having a further higher solubility is sought. Further, aconductive polymer composition composed of a substituted orunsubstituted polyaniline, a protonic acid and an organic solvent hasbeen reported (Japanese Unexamined Patent Publication (Kokai) No.2003-176409), but since the oxidizing agent/aniline (molar ratio) at thetime of polymerization of the aniline is 0.5, there is the problem thatthe yield of the polyaniline is 30 to 40%. When a molar ratio of anoxidizing agent/aniline is 1.0 or more, the dispersion stability becomesinsufficient. Further, attempts are being made to improve the solubilityby introducing a substituent into the side chain of the aniline, butthis is not for general use products, the yield is low and theconductivity is decreased, and therefore, this proposal is notpreferred. The solubility and dissolution of the polyaniline orpolyaniline derivative in an organic solvent referred to here indicatescoexistence of the state where fine particles of polyaniline or apolyaniline derivative are dispersed in an organic solvent and the statewhere polyaniline or a polyaniline derivative is dissolved in an organicsolvent.

A photovoltaic device is composed of a photoelectrode and a counterelectrode. In the past, as the counter electrode, an electrode composedof a platinum thin film formed on a transparent conductive glasssubstrate by vacuum vapor deposition or sputtering has been used.However, vacuum vapor deposition or sputtering requires expensive vacuumequipment. Further, the size of the substrate is strictly restricted, soit is difficult to form a platinum layer on a substrate of a large area.

The dye-sensitized solar cell was developed by Graetzel et al. ofSwitzerland. Among solar cells using organic materials, it has theadvantages that it is high in photovoltaic conversion efficiency and islower in manufacturing cost compared with silicon-based solar cells and,therefore, is gaining attention as a new type of solar cell.

FIG. 1 shows an example of the typical configuration of a dye-sensitizedsolar cell. Typical examples of a dye-sensitized solar cell include, aruthenium complex dye-sensitized type titanium dioxide solar cell.Explaining the configuration of a cell taking, as an example, thisruthenium complex dye-sensitized type titanium dioxide solar cell, shownin FIG. 1, a transparent substrate 11 such as glass is provided on onesurface with a transparent conducting layer 12. On the top thereof, anoxide semiconductor mesoporous film 13 is formed comprising oxidesemiconductor particles such as titanium dioxide and carrying aphotosensidizing dye (e.g., a ruthenium complex dye) to form aphotoelectrode 14. A counter electrode 15 is arranged facing thephotoelectrode 14. It is possible to arrange the electrolyte layer 16comprising an electrolyte comprising non-aqueous solution containing aredox of iodine/iodine ion, etc. between the photoelectrode 14 andcounter electrode 15.

In this dye-sensitized solar cell, when sunlight or other light strikesthe cell from the transparent substrate 11 side, electromotive force isgenerated between the photoelectrode 14 and counter electrode 15,electrons flow from the photoelectrode 14 to the counter electrode 15,and power is generated. The counter electrode 15 comprising a conductivesubstrate such as, metal substrate or a non-conductive substrate such asglass substrate on which a conducting layer such as platinum, gold,carbon is formed, or a non-conductive substrate such as glass substrateon which a conductive metal oxide film and a conducting layer such asplatinum, gold, carbon, are formed, or on a nonconductive substrate suchas a glass substrate, a conductive metal oxide film such asfluorine-doped tin oxide (FTO) and tin-doped indium oxide (ITO) and aconductive film such as platinum, gold and carbon are successivelylaminated. In particular, platinum has large catalytic action enablingsmooth injection of electrons from the counter electrode 15 to theelectrolyte 16, so a counter electrode 15 having a platinum thin film ismuch used.

A counter electrode 15 having a platinum thin film has conventionallybeen obtained forming a platinum thin film on a substrate by vacuumvapor deposition or sputtering (Japanese Unexamined Patent Publication(Kokai) No. 2000-173680 and Japanese Unexamined Patent Publication(Kokai) No. 2000-36330). However, platinum is an expensive preciousmetal more expensive than gold. When using sputtering or vacuum vapordeposition to form a counter electrode 15 having a platinum thin film,there is much waste in the consumption of materials, the productivity islow, a vacuum facility is required, the capital cost is high and theproduction cost becomes higher. Alternatively, a counter electrode 15having a platinum thin film may be formed by a method of dipping asubstrate into a platinum solution such as chloroplatinic acid solutionto coat the substrate with the platinum solution, then sintering it orby coating a platinum solution on a substrate by spraying, thensintering it. Both dipping and spraying may also be mentioned as simplemethods, since they do not require vacuum facilities, but to convert aplatinum solution coated on a substrate to a platinum thin film,sintering at about 400° C. is required, so there was the defect thatthis method cannot be applied to a substrate weak against heat.

Further, a counter electrode formed with a conductive polymer thin film,instead of a platinum thin film, has also been reported (JapaneseUnexamined Patent Publication (Kokai) No. 7-226527). As a method offorming a conductive polymer thin film, the method of usingelectrochemical polymerization to form a conductive polymer thin film ona conductive substrate or the method of coating a conductive polymerdispersion or solution on a substrate may be exemplified. Regarding the“conductive polymer solution” mentioned herein, the co-existence of thestate of conductive polymer particles dispersed in a solvent and thestate of a conductive polymer dissolved in a solvent is defined as a“conductive polymer solution” for brevity. Regarding the electrochemicalpolymerization, since the substrate which can be used is restricted to aconductive substrate or the area of the substrate which can be used isrestricted, it is difficult to form a large area conductive polymer thinfilm on the substrate. Further, as a conductive polymer particledispersion or conductive polymer solution, for example, an aqueouspoly(3,4-ethylenedioxythiophene) dispersion (Baytron P made by Bayer),an aqueous polyaniline solution (Aquasave made by Mitsubishi Rayon),etc. may be exemplified. However, the synthesis of a monomer istroublesome. Further, as a polyaniline solution, an N-methylpyrrolidonesolution of a polyaniline has been reported, but the method ofpreparation of the solution was troublesome or, since the polyanilinethin film obtained from a polyaniline solution is an insulator, anoperation for doping to convert it to a conductor is necessary and notsimple (Japanese Unexamined Patent Publication (Kokai) No. 3-28229 andU.S. Pat. No. 5,728,321). Further, an organic solvent dispersion of aconductive polyaniline has been reported in the Japanese UnexaminedPatent Publication (Kokai) No. 6-279584 or Japanese Unexamined PatentPublication (Kokai) No. 2003-277500, but the dispersability to anorganic solvent is not necessarily high (Japanese Unexamined PatentPublication (Kokai) No. 6-279584) or the method of preparation of thedispersion was troublesome. Further, the conductive polymer thin filmformed with the conductive polymer particle dispersion or conductivepolymer solution does not exhibit a performance as good as a platinumthin film.

SUMMARY OF THE INVENTION

The object of the present invention is to provide a method for producinga conductive polyaniline stably dispersed in an organic solvent at ahigh yield and a polymer composition containing the conductivepolyaniline obtained therefrom.

Another object of the present invention is to provide a conductivesubstrate able to be easily obtained inexpensively at a high yield,using a dispersion of a conductive polyaniline stably dispersed in anorganic solvent, and exhibiting a performance equal to or better than acounter electrode having a conventional platinum thin film.

A further object of the present invention is to provide a counterelectrode capable of forming at a low production cost under a lowtemperature, while having a performance equal to or better than acounter electrode having a conventional platinum thin film and toprovide a dye-sensitized solar cell using the same.

In accordance with the present invention, there is provided a method forproducing a conductive polyaniline stably dispersed in an organicsolvent comprising oxidative polymerizing aniline or its derivative inthe presence of at least one member selected from the group consistingof sulfonic acids and water-insoluble organic polymers having a protonicacid group in a mixed layer composed of an aqueous layer and organiclayer during which it establishes the presence of a molecular weightadjusting agent and, optionally, a phase transfer catalyst.

In accordance with the present invention, there is also provided aconductive polyaniline-containing organic polymer composition comprisinga conductive polyaniline obtained by the above method and an organicpolymer.

In accordance with the present invention, there is further provided aconductive substrate comprising, coated thereon, (A) polyaniline derivedfrom polymerization of aniline or aniline derivative, (B) sulfonic acidand/or (C) an organic polymer having a protonic acid group, (D) amolecular weight adjusting agent and (E) an organic solvent capable ofdissolving the sulfonic acid (B), the organic polymer having a protonicacid group (C) and the molecular weight adjusting agent (D).

In accordance with the present invention, there is still furtherprovided a photovoltaic device comprising (i) a photoelectrode composedof a transparent conducting layer and a metal oxide semiconductormesoporous film, (ii) a counter electrode located opposite to thephotoelectrode and (iii) an electrolyte layer containing a redox couplepresent between the both electrodes, wherein said counter electrode isformed by the conductive substrate mentioned above.

In accordance with the present invention, there is still furtherprovided a dye-sensitized solar cell comprising a metal oxidesemiconductor mesoporous film of the counter electrode mentioned aboveand a photosensitizing dye carried thereon.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view of an example of the basic configuration of adye-sensitized solar cell of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

The singular form (“a”, “an” and “the”) used in the presentspecification and the attached “claims” should be understood asincluding the plural form, except when otherwise clear it does not fromthe context.

In the present invention, when producing polyaniline, it is possible tosynthesize conductive polyaniline stably dispersed in an organic solventat a high yield by establishing the presence of a molecular weightadjusting agent and, when necessary, a phase transfer catalyst in thepresence of a sulfonic acid compound and/or a polymer compound having aprotonic acid group. Further, when mixing the polyaniline obtained withSBR in a toluene solution, the electroconductivity of a compositioncontaining 5 wt % of polyaniline, based upon the weight of SBR, is 10⁻⁵Scm⁻¹ and a rubber composition exhibiting a sufficient staticelectricity removing effect is obtained.

The conductive polyaniline soluble in an organic solvent according tothe present invention is normally obtained by oxidative polymerizationof aniline or its derivative or any mixture thereof.

As the above aniline derivative, an aniline derivative having at leastone alkyl group, alkenyl group, alkoxy group, alkylthio group, arylgroup, aryloxy group, alkylaryl group, arylalkyl group and alkoxyalkylgroup, as a substituent, at a position other than the 4th position maybe mentioned. Preferably, an aniline derivative having at least one C₁to C₅ alkyl group, alkoxy group, alkoxyalkyl group, preferably a C₆ toC₁₀ aryl group, as a substituent, may be mentioned.

The oxidizing agent for the above oxidative polymerization is notparticularly limited so long as it can polymerize the above aniline orits derivative. For example, ammonium persulfate, persulfuric acid,sodium persulfate, potassium persulfate and other persulfates, hydrogenperoxide, ferric chloride, ferric sulfate, potassium bichromate,potassium permanganate, hydrogen peroxide-ferrous salt and other redoxinitiators, etc. may be preferably used. These oxidizing agents may beused alone or in any combination of two or more types. The amount of theoxidizing agent usable in the present invention is not particularlylimited so long as it is an amount capable of oxidatively polymerizingthe above aniline or its derivative, but is preferably 0.01 to 10 moles,more preferably 0.1 to 5 moles, based upon 1 mole of aniline or itsderivative.

The present invention oxidatively polymerizes the aniline or itsderivative in the presence of a molecular weight adjusting agent and,when necessary, a phase transfer catalyst in the presence of a sulfonicacid compound and/or an organic polymer compound having a protonic acidgroup. The polymerization is carried out in a mixed layer of an aqueouslayer and an organic layer.

As the sulfonic acid usable in the present invention, it is possible touse any sulfonic acid used for oxidative polymerization of aniline inthe past, specifically an aliphatic or aromatic sulfonic acid having oneor more sulfonic acid groups and their salts such as an alkylsulfonicacid, arylsulfonic acid, alkylarylsulfonic acid, α-olefin sulfonic acid,a sulfonic acid of a higher fatty acid ester, (di)alkylsulfosuccinicacid, a sulfonic acid of a higher fatty acid amide, camphorsulfonic acidand salts thereof. The amount of use of these sulfonic acids is notparticularly limited, but use of 0.01 to 5 moles based upon 1 mole ofaniline or its derivative is preferable and use of 0.1 to 3 moles ismore preferable. At the time of polymerization, in addition to thesulfonic acid, it is also possible to add hydrochloric acid, sulfuricacid, nitric acid, perchloric acid or another inorganic acid,m-nitrobenzoic acid, trichloroacetic acid or another organic acid oranother protonic acid, if necessary.

The water-insoluble organic polymer compound having a protonic acidgroup usable in the present invention has a structure where a pluralityof side chains having protonic acid groups and a plurality of sidechains exhibiting affinity with an organic solvent are bonded to themain chain. The protonic acid groups are not limited to the side chainends and a plurality thereof may also be present in the middle of theside chains. As the protonic acid group, a sulfonic acid group, acarboxyl group, a phosphoric acid group or a sulfuric acid group may bementioned. Preferably, there is a sulfonic acid group, carboxyl group orphosphoric acid group. The water-insoluble polymer compound having aprotonic acid group is not particularly limited so long as it satisfiesthe above structure, but a copolymer of an ethylenic unsaturated monomerhaving a protonic acid group and an ethylenic unsaturated monomer havinga side chain exhibiting affinity with an organic solvent may bementioned. As an ethylenic unsaturated monomer having a protonic acidgroup, styrenesulfonic acid, vinylsulfonic acid, allylsulfonic acid,methalyl sulfonic acid, 2-methacryloyloxyethyl-1-sulfonic acid,3-methacryloyloxypropane-1-methyl-1-sulfonic acid,3-methacryloyloxypropane-1-sulfonic acid,4-methacryloyloxybutane-1-sulfonic acid, 2-acrylamido-2-methylpropanesulfonic acid, methalyloxybenzene sulfonic acid, methalyl sulfonic acid,acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaricacid, crotonic acid, monobutyl fumarate, monobutyl maleate,monoethylhexyl maleate, hydroxypropyl maleate, maleate anhydride,citraconic acid anhydride, ethyl(meth)acrylate phosphate,polyoxyethyleneglycol mono(meth)acrylate phosphate, or propyleneglycolmono(meth)acrylate phosphate may be mentioned. Further, the protonicacid group of the ethylenic unsaturated monomer having these protonicacid groups may also be an ammonium group, alkali metal salt or salt ofan organic amine group. As the ethylenic unsaturated monomer having aside chain exhibiting affinity with the organic solvent, styrene,α-methylstyrene, chlorostyrene, 1,3-butadiene, isoprene,2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, vinyl chloride, vinylidenechloride, (meth)acrylonitrile, a styrene derivative having a C₁ to C₃₀,hetero atom-includable hydrocarbon group, a (meth)acrylic acid esterderivative, a (meth)acrylamicde derivative, a vinyl ether derivative, ora carboxylic acid vinyl ester derivative may be mentioned. The abovecopolymer may be any of a random copolymer, block copolymer or graftcopolymer. The above polymer may be obtained by using a knownpolymerization method.

As the water-insoluble organic polymer compound having a protonic acidgroup, it is possible to use a commercially available water-insolublepigment dispersant. As such commercially available products, forexample, Disperbyk 110, Disperbyk 111, Disperbyk 171, Disperbyk 174,BYK-P104 (made by BYK Chemie), Solsperse 26000, Solsperse 32000 (made byAvesia), etc. may be mentioned. The amount of the organic polymercompound having these protonic acid groups used is not particularlylimited, but preferably an organic polymer compound is used so that theprotonic acid group becomes a ratio of 0.05 to 20 moles with respect toone mole of the aniline or the derivative, more preferably 0.1 to 10moles is used.

As the molecular weight adjusting agent used in the present invention,an aniline derivative having a substituent at the 4th position, a thiolcompound, a disulfide compound and/or an α-methylstyrene dimer may bementioned.

As the aniline derivative having a substituent X at the 4th position, acompound of formula (I) may be mentioned:

In formula (I), X indicates an alkyl group, alkenyl group, alkoxy group,alkylthio group, aryl group, aryloxy group, alkylaryl group, arylalkylgroup, alkoxyalkyl group, or halogen group, Y indicates a hydrogen atom,alkyl group, alkenyl group, alkoxy group, alkylthio group, aryl group,aryloxy group, alkylaryl group, arylalkyl group, alkoxyalkyl group, orhalogen group, and n indicates an integer of 0 to 4, where when n is aninteger of 2 to 4, Y may be the same or different. A preferablesubstituent X is a C₁ to C₅ alkyl group, alkoxy group, alkoxyalkylgroup, or C₆ to C₁₀ aryl group. A preferable substituent Y is a hydrogenatom, a C₁ to C₅ alkyl group, alkoxy group, alkoxyalkyl group, or C₆ toC₁₀ aryl group.

As the thiol compound and/or disulfide compound used in the presentinvention, butyl mercaptan, octyl mercaptan, dodecyl mercaptan,hexadecyl mercaptan, tetradecyl mercaptan,2,2,4,6,6-pentamethylheptane-4-methylenethiol, and other thiolcompounds, diethyl disulfide, dibutyl disulfide, and other alkyldisulfides, diphenyl disulfide, dibenzyl disulfide, and other aromaticdisulfides, dimethyl xanthogen disulfide, diethyl xanthogen disulfide,and other xanthogen disulfides, tetramethyl thiuram disulfide,tetraethyl thiuram disulfide, and other thiuram disulfides and otherdisulfide compounds may be mentioned. These are known compounds and mostare generally commercially available. The amount of the molecular weightadjuster used is not particularly limited, but use of 5.0×10⁻⁵ to5.0×10⁻¹ moles per 1 mole of the aniline or its derivative ispreferable, while the use of 2.0×10⁻⁴ to 2.0×10⁻¹ moles is morepreferable.

The phase transfer catalyst usable in the preferable embodiment of thepresent invention is not particularly limited so long as it is generallyused as a phase transfer catalyst, but specificallybenzyltriethylammonium chloride, methyltrioctylammonium chloride,tetra-n-butylammonium bromide, tetra-n-butylammonium iodide,tetra-n-butylammonium chloride, and other tetraalkylammonium halides;tetrabutylammonium hydroxide and other tetraalkylammonium hydroxides;methyltriphenylphosphonium bromide and other tetraalkylphosphoniumhalides; 12-crown-4,15-crown-5,18-crown-6 and other crown ethers etc.may be mentioned. Among these, tetraalkylammonium halides are preferablein terms of ease of handling such as removal of the catalyst after thereaction. In particular, the industrially inexpensively availabletetra-n-butylammonium bromide or tetra-n-butylammonium chloride ispreferable. In the present invention, the amount of the phase transfercatalyst used, when necessary, is not particularly limited, but ispreferably at least 0.0001 molar times of the oxidizing agent, morepreferably at least 0.005 molar times, but if the phase transfercatalyst is used in excess, the isolation and refining processes afterthe end of the reaction become difficult, and therefore, when used, itis preferably used in a range of 5 molar times or less, more preferablyequal molar times or less.

Regarding the method of oxidative polymerization of the aniline or itsderivative according to the present invention, other than making use ofthe above reaction ingredients as essential requirements, it is possibleto employ methods as used in the past. Other conventional additives mayalso be used as in the past in so far as they do not detract from theobject of the present invention. The polymerization medium of thepresent invention uses two types of liquid media, that is, water and anorganic solvent, as solvents. The organic solvent is not particularlylimited so long as it dissolves aniline or its derivative and is notwater-soluble. As specific examples, benzene, toluene, xylene, or otheraromatic hydrocarbons; hexane, heptane, octane, or other aliphatichydrocarbons; dichloroethane, chloroform, 1,2-dichloroethane,chlorobenzene, dichlorobenzene, and other halogenated hydrocarbons;diethyl ether, di-n-propyl ether, diisopropyl ether, di-n-butyl ether,tert-butylmethyl ether, and other ethers; ethyl acetate, n-propylacetate, isopropyl acetate, n-butyl acetate, and other esters may bementioned. Among these, aromatic hydrocarbons, aliphatic hydrocarbons,and halogenated hydrocarbons are preferable, while the inexpensive andlow toxicity toluene and xylene are particularly preferable. The aboveorganic solvents may be used in combinations of two or more types mixedtogether. As the amount of the liquid medium used, any stirrable amountis possible. Normally, 1 to 500 times by weight of the aniline or itsderivative, preferably 2 to 300 times by weight is used. Here, theamount of the organic solvent used is 0.05 to 30 times by weight of thewater, preferably 0.1 to 10 times by weight of water.

The reaction temperature is not particularly limited, but preferably is−10° C. to 80° C. The polyaniline oxidative polymerized according to thepresent invention is extremely high in yield, normally 80% or more.Further, the electroconductivity is 10⁻⁹ Scm⁻¹ or more.

The polyaniline stably dispersed in an organic solvent of the presentinvention may be isolated by the following procedures:

(a) The method of isolating aniline by removing the organic solvent fromthe reaction solution obtained by evaporation etc. to cause thepolyaniline to precipitate, then removing the water.

(b) The method of isolating polyaniline dispersed in an organic solventby adding water and/or a polar organic solvent to the reaction solutionobtained and removing only the water from the reaction solutionseparated into the organic layer and aqueous layer.

(c) The method of isolating polyaniline by adding an excess of a polarorganic solvent to the reaction solution obtained to cause polyanilineto precipitate, then using filtration or decantation etc. to remove thesolvent.

Among these, the preferable methods of isolation are the methods of (a)and (b). The more preferable one is the method of (b).

Further, a polyaniline dispersion may also be prepared by the followingprocedures in addition to the above method (b).

(d) The method of dispersing the polyaniline isolated by (a) or (c) inthe organic solvent used when oxidative polymerizing aniline or ananiline derivative.

(e) The method of adding the organic solvent used when preparing thedispersion and/or an organic solvent soluble with this organic solventto the polyaniline dispersion prepared by the method of (b).

When preparing the above polyaniline dispersion, a sand mills beadsmill, ball mill, triple roll mill, colloid mill, ultrasonic homogenizer,Henschel mixer, jet mill or other disperser may also be used.

The organic polymer composition according to the present invention isobtained by preferably blending 0.01 to 100 parts by weight of aconductive polyaniline, more preferably 0.05 to 80 parts by weight,based upon 100 parts by weight of an organic polymer composition. If theamount blended is too small, the conductivity of the organic polymercomposition is liable to become 10⁻¹² Scm⁻¹ or less. Conversely, if toolarge, an effect commensurate with the amount added may not be able tobe obtained.

The organic polymer usable in the organic polymer composition of thepresent invention is not particularly limited, but as preferableexamples, natural rubber, isoprene rubber, nitrile rubber (e.g.,acrylonitrile-butadiene rubber, acrylonitrile-styrene-butadiene rubber,etc.), hydrogenated nitrile rubber, butadiene rubber, styrene-butadienerubber, butyl rubber, halogenated butyl rubber, ethylene-α-olefin rubber(e.g., ethylene-propylene rubber, ethylene-propylene-nonconjugated dienerubber, ethylene-butene-nonconjugated diene rubber, etc.),polynorbornene rubber, acryl rubber, fluororubber, silicone rubber,ethylene-vinyl acetate rubber, epichlorohydrin rubber,epichlorohydrin-ethylene oxide copolymer rubber, chlorinatedpolyethylene rubber, chloroprene rubber, chlorosulfonated polyethylenerubber, fluororubber, polyurethane rubber or other rubber, polyethylene,polypropylene or other polyolefin resin, polyethylene terephthalate,polyethylene naphthalate, polybutylene terephthalate or other polyesterresin, nylon 6 or nylon 6,6 or other polyamide resin, bisphenol A-typeepoxy resin, novolac type epoxy resin or other epoxy resin, polyamideimide, polyamic acid or other polyimide resin, polyfluorovinylidene orother fluororesin, modified PPE resin, polycarbonate resin, polyacetalresin or modified products thereof or other resins etc. may bementioned.

The method for mixing the organic polymer and conductive polyaniline isnot particularly limited. For example, the method for mixing polyanilineisolated by the above procedures (a) and (c) and an organic polymer by akneader may be mentioned. As a kneader, a roll, kneader, Bambury mixer,twin-screw extruder, etc. may be mentioned. Further, it may be obtainedby mixing the polyaniline dispersion isolated by the above procedure(b), (d) and (e) and the organic polymer. The organic polymer mixed maybe dissolved or dispersed in a solvent in advance. The solvent is notparticularly limited, but a solvent having solubility with the solventused when preparing the polyaniline dispersion is preferable. The mixingmethod is not particularly limited so long as the polyaniline andorganic polymer can be efficiently mixed, but the simple agitation andmixing method and the method for mixing using a sand mill, beads mill,ball mill, triple roll mill, colloid mill, ultrasonic homogenizer,Henschel mixer, jet mill, or other disperser may also be mentioned. Whenmixing a solid organic polymer and polyaniline dispersion, it is alsopossible to use the above kneader. Further, the organic polymercomposition of the present invention may also be obtained by mixing withthe above organic polymer the polyaniline and/or polyaniline dispersionobtained by the above technique and a plasticizer and process oilgenerally used for improving the processability and flexibility oforganic polymers mixed in advance. Further, the organic polymercomposition may also be obtained by mixing with the above organicpolymer the polyaniline and/or polyaniline dispersion obtained by theabove technique and carbon black, silica, talc or other filler used as afiller for the above organic polymer mixed in advance. Further, theorganic polymer composition of the present invention may also beobtained by mixing with the above organic polymer the polyaniline and/orpolyaniline dispersion obtained by the above technique treating theabove filler on its surface.

The organic polymer composition according to the present invention mayinclude as other ingredients, for example, carbon black, silica, talc oranother filler, a vulcanization or cross-linking agent, a vulcanizationor cross-linking accelerator, a silane coupling agent, various types ofoils, an antioxidant, a UV absorbent, an optical stabilizer, a flameretardant, a plasticizer, or other various types of additives generallyblended into rubber or resins in the conventional blended amounts. Theorganic polymer composition according to the present invention may alsoinclude, as other ingredients, an ion conducting agent, an electronconducting agent, etc. As an ion conducting agent, for example, aquaternary ammonium salt, a borate, a surfactant, etc. may be mentioned.As an electron conducting agent, conductive zinc oxide, conductivetitanium oxide, conductive stannous oxide, graphite, etc. may bementioned.

According to a further aspect of the present invention, the conductivesubstrate having a performance equal to or better than a counterelectrode having a conventional platinum thin film can be obtained bythe use of the above conductive polyaniline dispersion stably dispersedin an organic solvent and capable of producing at a high yield and at alow cost.

The inventors previously made it possible, when producing a polyaniline(A) from an aniline or aniline derivative, to synthesize a conductivepolyaniline able to be stably dispersed in an organic solvent byoxidative polymerization together with a molecular weight adjustingagent (D) in the presence of an organic sulfonic acid (B) and/or highmolecular weight polymer having a protonic acid group (C). The inventorsengaged in further research and succeeded in coating this polyanilinedispersion on a transparent conductive glass substrate comprised of anFTO glass (glass formed on one surface with a fluorine-doped tin oxidetransparent conducting layer) substrate, drying it, and thereby laying apolyaniline (PAn) conducting layer on an FTO glass substrate tofabricate an FTO-PAn electrode. The inventors found that adye-sensitized solar cell having this FTO-PAn electrode as a counterelectrode, compared with a cell using only FTO glass as a counterelectrode, becomes larger in short-circuit photocurrent and open-circuitphotovoltage and higher in energy conversion efficiency.

The polyaniline (A) forming the conductive polyaniline dispersionaccording to the present invention can be obtained by oxidativepolymerization of an aniline or its derivative or any mixture thereof,as mentioned above. The other components are also available, asmentioned above.

According to the present invention, a dispersion of an organic solvent(E) including the components (A), (B) and/or (C) and (D) may be coatedon a conductive substrate by an ordinary method, for example, a knownwet type film formation method, so as to form a conductive polyanilinethin film on a substrate having a transparent conducting layer. The wettype film formation method is not particularly limited. For example,screen printing, injection printing, roll coating, doctor blade coating,spin coating, spray coating, etc. may be mentioned. It is possible touse this method to coat the dispersion to a thickness of, for example,0.01 to 100 μm to obtain a conductive substrate according to the presentinvention. The concentrations of the ingredients in the dispersion arenot particularly limited, but from the viewpoints of the dispersionstability of the polyaniline dispersion and the conductivity andstrength of the polyaniline thin film formed from the dispersion, 0.01to 90 wt % of the polyaniline (A), 0 to 80 wt % of the sulfonic acid(B), 0 to 80 wt % of the organic polymer having a protonic acid group(C), and 0.01 to 20 wt % of the molecular weight adjusting agent (D) arepreferable.

As the conductive substrate to be coated with the polyaniline dispersionof the present invention, as in the past, for example, a metal, a glassor resin substrate having a conducting layer on the surface, etc. may beused. As the metal, except for platinum, a metal such as gold, silver,copper, aluminum, indium, titanium may be used. Examples of the resinsubstrate are polymethylmethacrylate, polycarbonate, polystyrene,polyethylene sulfide, polyether sulfone, polyolefin, polyethyleneterephthalate, polyethylene naphthalate, polyarylate, polyimide,triacetyl cellulose, etc. As the conducting layer provided on thesurface, except for platinum, gold, silver, copper, aluminum, indium,titanium and other metal, ruthenium oxide, antimony- or fluorine-dopedtin oxide, aluminum- or potassium-doped zinc oxide, tin-doped indiumoxide, or other conductive metal oxide, carbon, etc. may be mentioned.The thickness of the conducting layer is preferably 0.01 to 10 μm or so.The method of provision of the conducting layer may be a conventionalmethod. For example, coating, sputtering, vacuum vapor deposition, spraypyrolysis, chemical vapor deposition (CVD), sol gel, etc. may bementioned.

The conductive substrate of the present invention is obtained by coatingthe above-mentioned conductive substrate with a polyaniline dispersion,but it is also possible to coat a non-conductive substrate comprised ofa glass or resin substrate directly with a polyaniline dispersion anduse it as a conductive substrate.

The conductive substrate according to the present invention may be usedfor a photovoltaic device or dye-sensitized solar cell instead of acounter electrode having a conventional platinum thin film.

A photovoltaic device and dye-sensitized solar cell shown in FIG. 1 willnow be explained.

The photoelectrode 14 is composed of a transparent substrate 11, atransparent conducting layer 12 and an oxide semiconductor mesoporousfilm 13. The transparent substrate 11 may be a glass substrate or aresin substrate such as polystyrene, polyethylene, polypropylene,polyethylene terephthalate, polyethylene naphthalate, polycarbonate,polyphenylenesulfide, cyclic olefin polymer, polyether sulfone,polyallylate, triacetyl cellulose. One having a good light transmissionproperty is good.

As the transparent conducting layer 12, a conductive metal oxide such asantimony- or fluorine-doped tin oxide, aluminum- or gallium-doped zincoxide, tin-doped indium oxide may be mentioned. The thickness of theconducting layer is preferably 0.01 to 10 μm or so. The method forproviding the conducting layer may be a conventional method. Forexample, coating, sputtering, vacuum vapor deposition, spray pyrolysis,chemical vapor deposition (CVD), sol gel, etc. may be mentioned.

The oxide semiconductor mesoporous film 13 can be obtained by coating adispersion of oxide semiconductor particles on a transparent conductinglayer 12. As the oxide semiconductor particles, titanium oxide, tinoxide, zinc oxide, tungsten oxide, zirconium oxide, hafnium oxide,strontium oxide, vanadium oxide, niobium oxide, etc. may be mentioned.These may be used alone or in any combination thereof. The dispersion ofthe oxide semiconductor particles can be obtained by mixing thesemiconductor particles and the dispersion medium by a dispersion mixersuch as sand mill, beads mill, ball mill, triple roll mill, colloidmill, ultrasonic homogenizer, Henschel mixer, jet mill. Further, toprevent reagglomeration of particles in the dispersion, acetyl acetone,hydrochloric acid, nitric acid, a surfactant, a chelating agent, etc.may also be added. Further, for the purpose of thickening thedispersion, a polymer such as polyethylene oxide or polyvinyl alcohol, acellulose-based thickening agent and various other types of thickeningagents may be added.

As a semiconductor particle dispersion, a commercially available product(titanium dioxide paste SP100, SP200 made by Showa Denko, Ti-Nanoxide-T,Ti-Nanoxide-D made by Solaronix, PECC01 made by Peccell Technologies)may be used. As the method for coating the dispersion of thesemiconductor particles on the transparent conducting layer, for examplea known wet type film formation method may be used. The wet type filmformation method is not particularly limited. For example, dipping, spincoating, casting, die coating, roll coating, doctor blade coating, barcoating, etc. may be mentioned.

Further, it is preferable to coat the dispersion of the oxidesemiconductor particles on a transparent conducting layer, then performheat treatment, chemical treatment, or plasma or ozone treatment for thepurpose of improving the electronic contact between particles, improvingthe bondability with the transparent conducting layer and improving thefilm strength. The temperature of the heat treatment is preferably 40°C. to 700° C., more preferably 40° C. to 650° C. Further, the treatmenttime is not particularly limited, but usually is 10 seconds to 24 hours.As the chemical treatment, chemical plating using an aqueous titaniumtetrachloride solution, chemical plating using a carboxylic acidderivative, electrochemical plating using an aqueous titaniumtrichloride solution, etc. may be mentioned.

Further, the photovoltaic device comprising a photosensidizing dyecarried on the oxide semiconductor mesoporous film 13 is adye-sensitized solar cell. The photosensidizing dye is not particularlylimited so long as it is a dye which has absorption in the visible lightregion and/or infrared light region. A metal complex, organic dye, etc.may be used. Specifically, a ruthenium complex dye with a ligand such asa bipyridine structure or a terpyridine structure, a porphyrin-baseddye, a phthalocyanine-based dye, a cyanine-based dye, amerocyanine-based dye, a xanthene-based dye, etc. may be used. Thecarrying method is not particularly limited, but the dye may be carriedby, for example, dissolving it in water or alcohol and dipping themesoporous film 13 in the dye solution or coating the dye solution onthe mesoporous film. As a ruthenium complex dye, a commerciallyavailable product (Ruthenium 535, Ruthenium 535 bis-TBA made bySolaronix, PECD03, PECD07 made by Peccell Technologies) may be used.

As the electrolyte for forming an electrolyte layer 16, an organicsolvent and/or inonic liquid containing a redox couple. As the organicsolvent, acetonitrile, methoxyacetonitrile, propionitrile, ethylenecarbonate, propylene carbonate, γ-butyralactone are exemplified. As theionic liquid, imidazolium salts, pyridinium salts, pyrrolidinium saltsmay be exemplified (see Hiroyuki Ohno, “Kogyo Zairyo (in Japanese)” 48,39 (2000), “Ionic Liquid—Updated Condition and Future of Development”edited by Hiroyuki Ohno, CMC publisher (2003), etc). Preferable examplesare imidazolium cation and iodide ion or bistrifluoromethylsulfonylimide anion.

The redox couple included in the electrolyte is not specificallylimited. Examples are iodine/iodide ion, bromine/bromide ion. Forexample, iodine and a metal iodide such as LiI, NaI, KI, iodine andiodide of quaternary imidazolium compound, iodide of quaternarypyrridinium compound, iodide of tetraalkyl ammonium compound and otheriodine/iodide ion pairs as well as bromine and metal bromide such asLiBr, NaBr, KBr, bromine and a bromide of quaternary imidazoliumcompound, a bromide of quaternary pyrridinium compound, bromide oftetraalkyl ammonium compound and other bromine/bromide ion pairs, metalcomplexes such as ferrocyanic acid salt-ferricyanic acid salt,ferrocene-ferricinium salt, a sulfur compound such as disulfide compoundand mercapto compound, hydroquinone and quinone, etc. The redox coupleof iodine and iodide ion is preferable. These redox couples may be usedalone or in any combination thereof.

In addition, inorganic or organic salts may be added for the purpose ofimproving a short-circuit photocurrent of the photovoltic device. Thepreferable inorganic or organic salts include, for example, alkali metalsalts and alkaline earth metal salts. Examples of such inorganic saltsare lithium iodide, sodium iodide, potassium iodide, magnesium iodide,calcium iodide, lithium trifluoroacetate, sodium trifluoroacetate,lithium thiocyanate, lithium tetrafluoroborate, lithiumhexafluorophosphate, lithium perchlorate, lithiumtrifluoromethanesulfonate, lithium bis(trifluoromethane sulfonyl)imide.These salts may be used alone or in any combination thereof. Further,for the purpose of improving an open-circuit photovoltage of thephotovoltic device, pyridines, benzimidazoles, etc. may be added.Typical examples are alkylpyridines such as methylpyridine,ethylpyridine, propylpyridine, butylpyridine, etc., alkylimidazoles suchas methylimidazole, ethylimidazole, propylimidazole, etc. These may beused alone or in any combination thereof.

The amounts to be added of the above salts, pyrididines, benzimidazoles,etc. are not specifically limited, unless the objects of the presentinvention are adversely affected.

The electrolyte may be gelled with the addition of a gelling agentthereto.

Furthermore, solid positive hole transportion material such as p-typesemiconductor may be used, instead of the electrolyte, for theelectrolyte layer 16. As the p-type semiconductor, copper (I) compoundssuch as copper (I) iodide, copper (I) thiocyanide are exemplified.

EXAMPLES

The present invention will now be explained in further detail byExamples, but the present invention is not limited to these Examples.

Examples of Preparation Preparation of Polyaniline 1 (ConductivePolyaniline Dispersion)

In 100 g of toluene, as shown in Table I, 2 g of aniline, 4.2 g ofdodecylbenzene sulfonic acid, 1.0 g of polyacrylic acid derivative(Solsperse 26000, made by Avecia), and 0.03 g of 4-methylaniline weredissolved, then 50 g of distilled water in which 3.58 ml of 6Nhydrochloric acid was dissolved was added. 180 mg of tetrabutylammoniumbromide was added to the mixed solution, the result was cooled to 5° C.or less, then 30 g of distilled water in which 5.4 g of ammoniumpersulfate was dissolved was added. The resultant mixture was oxidativepolymerized in the state of 5° C. or less for 5 hours, then the toluenewas distilled off in vacuo. The polyaniline precipitate formed in thewater was obtained by filtration, then was rinsed with water to obtainthe intended Polyaniline 1. The polyaniline obtained was dispersed in150 g of toluene, then the aqueous layer was removed to thereby obtain apolyaniline toluene dispersion. Part of the polyaniline toluenedispersion was taken and the toluene distilled off in vacuo, whereuponthe dispersion contained 4.1 wt % solid (polyaniline content 1.3 wt %).This dispersion was filtered by a filter having a pore size of 1.0 μm,whereupon there was no clogging. The dispersion was stable and did notcoagulate or precipitate, even after the elapse of six months at roomtemperature. From the elemental analysis, the molar ratio per anilinemonomer unit of dodecylbenzene sulfonic acid was 0.45 and the yield ofthe polyaniline was 97%. Further, the electroconductivity determined bydistilling off the toluene in vacuo from the dispersion, preparingpellets by a compression molding machine and measuring by the four-probemethod at room temperature was 0.25 Scm⁻¹.

Preparation of Polyaniline 2

In 100 g of toluene, as shown in Table I, 2 g of aniline, 4.2 g ofdodecylbenzene sulfonic acid, 1.0 g of polyacrylic acid derivative(Solsperse 26000, made by Avecia), and 0.03 g of 4-methylaniline weredissolved, then 50 g of distilled water in which 3.58 ml of 6Nhydrochloric acid was dissolved was added. 180 mg of tetrabutylammoniumbromide was added to the mixed solution, the result was cooled to 5° C.or less, then 30 g of distilled water in which 5.4 g of ammoniumpersulfate was dissolved was added. The resultant mixture was oxidativepolymerized in the state of 5° C. or less for 5 hours, then the 50 g oftoluene and then a methanol-water mixed solvent (water/methanol=2/3(weight ratio)) were added and the resultant mixture was stirred. Afterthe end of stirring, only the aqueous layer was removed from thereaction solution separated into the organic (toluene) layer and aqueouslayer, whereby a polyaniline toluene dispersion was obtained. Part ofthe polyaniline toluene dispersion was taken and the toluene distilledoff in vacuo, whereupon the dispersion contained 4.1 wt % solid(polyaniline content 1.3 wt %). This dispersion was filtered by a filterhaving a pore size of 1.0 μm, whereupon there was no clogging. Thedispersion was stable and did not coagulate or precipitate, even afterthe elapse of six months at room temperature. From the elementalanalysis, the molar ratio per aniline monomer unit of dodecylbenzenesulfonic acid was 0.45 and the yield of the polyaniline was 96%.Further, the electroconductivity determined by distilling off thetoluene in vacuo from the dispersion, preparing pellets by a compressionmolding machine, and measuring by the four-probe method at roomtemperature was 0.26 Scm⁻¹.

Preparation of Polyaniline 3

Except for using, as the molecular weight adjusting agent, 0.05 g ofdodecane thiol, instead of 4-methylaniline, the same procedure wasfollowed as the preparation of Polyaniline 2 to obtain a polyanilinetoluene dispersion. Part of the polyaniline toluene dispersion was takenand the toluene distilled off in vacuo, whereupon the dispersioncontained 4.1 wt % solid (polyaniline content 1.3 wt %). This dispersionwas filtered by a filter having a pore size of 1.0 μm, whereupon therewas no clogging. The dispersion was stable and did not coagulate orprecipitate, even after the elapse of six months at room temperature.From the elemental analysis, the molar ratio per aniline monomer unit ofdodecylbenzene sulfonic acid was 0.45 and the yield of the polyanilinewas 95%. Further, the electroconductivity determined by distilling offthe toluene in vacuo from the dispersion, preparing pellets by acompression molding machine, and measuring by the four-probe method atroom temperature was 0.25 Scm⁻¹.

Preparation of Polyaniline 4

Except for using, as the molecular weight adjusting agent, 0.05 g ofα-methylstyrene dimer, instead of 4-methylaniline, the same procedurewas followed as the preparation of Polyaniline 2 to obtain a polyanilinetoluene dispersion. Part of the polyaniline toluene dispersion was takenand the toluene distilled off in vacuo, whereupon the dispersioncontained 4.1 wt % solid (aniline content 1.3 wt %). This dispersion wasfiltered by a filter having a pore size of 1.0 μm, whereupon there wasno clogging. The dispersion was stable and did not coagulate orprecipitate, even after the elapse of six months at room temperature.From the elemental analysis, the molar ratio per aniline monomer unit ofdodecylbenzene sulfonic acid was 0.45 and the yield of the polyanilinewas 96%. Further, the electroconductivity determined by distilling offthe toluene in vacuo from the dispersion, preparing pellets by acompression molding machine, and measuring by the four-probe method atroom temperature was 0.25 Scm⁻¹.

Preparation of Polyaniline 5

Without using a polyacrylic acid derivative, the same procedure wasfollowed as the preparation of Polyaniline 2 to obtain a polyanilinetoluene dispersion. Part of the polyaniline toluene dispersion was takenand the toluene distilled off in vacuo, whereupon the dispersioncontained 3.4 wt % solid (polyaniline content 1.3 wt %). This dispersionwas filtered by a filter having a pore size of 1.0 μm, whereupon therewas no clogging. The dispersion was stable and did not coagulate orprecipitate, even after the elapse of six months at room temperature.From the elemental analysis, the molar ratio per aniline monomer unit ofdodecylbenzene sulfonic acid was 0.45 and the yield of the polyanilinewas 96%. Further, the electroconductivity determined by distilling offthe toluene in vacuo from the dispersion, preparing pellets by acompression molding machine, and measuring by the four-probe method atroom temperature was 0.25 Scm⁻¹.

Preparation of Polyaniline 6

Without using dedecylbenzene sulfonic acid, the same procedure wasfollowed as the preparation of Polyaniline 2 to obtain a polyanilinetoluene dispersion. Part of the polyaniline toluene dispersion was takenand the toluene distilled off in vacuo, whereupon the dispersioncontained 2.0 wt % solid (polyaniline content 1.3 wt %). This dispersionwas filtered by a filter having a pore size of 1.0 μm, whereupon therewas no clogging. The dispersion was stable and did not coagulate orprecipitate, even after the elapse of three months; at room temperature.The yield of the polyaniline was 96%. Further, the electroconductivitydetermined by distilling off the toluene in vacuo from the dispersion,preparing pellets by a compression molding machine, and measuring by thefour-probe method at room temperature was 0.21 Scm⁻¹.

Preparation of Polyaniline 7

Without using tetrabutylammonium bromide, the same procedure wasfollowed as the preparation of Polyaniline 2 to obtain a polyanilinetoluene dispersion. Part of the polyaniline toluene dispersion was takenand the toluene distilled off in vacuo, whereupon the dispersioncontained 2.7 wt % solid (polyaniline content 0.8 wt %). This dispersionwas filtered by a filter having a pore size of 1.0 μm, whereupon therewas no clogging. The dispersion was stable and did not coagulate orprecipitate even after the elapse of six months at room temperature.From the elemental analysis, the molar ratio per aniline monomer unit ofdodecylbenzene sulfonic acid was 0.45 and the yield of the polyanilinewas 60%. Further, the electroconductivity determined by distilling offthe toluene in vacuo from the dispersion, preparing pellets by acompression molding machine, and measuring by the four-probe method atroom temperature was 0.25 Scm⁻¹.

Preparation of Polyaniline 8

Without using 4-methylaniline or tetrabutylammonium bromide, the sameprocedure was followed as the preparation of Polyaniline 2 to obtain apolyaniline toluene dispersion. Part of the polyaniline toluenedispersion was taken and the toluene distilled off in vacuo, whereuponthe dispersion contained 2.7 wt % solid (polyaniline content 0.7 wt %).This dispersion was filtered by a filter with a pore size of 1.0 μm,whereupon there was no clogging. The dispersion was allowed to stand atroom temperature for six months, whereupon a precipitate of thepolyaniline was formed. From the elemental analysis, the molar ratio peraniline monomer unit of dodecylbenzene sulfonic acid was 0.45 and theyield of the polyaniline was 55%. Further, the electroconductivitydetermined by distilling off the toluene in vacuo from the dispersion,preparing pellets by a compression molding machine, and measuring by thefour-probe method at room temperature was 0.20 Scm⁻¹.

TABLE I Poly- Poly- Poly- Poly- Poly- Poly- Poly- Poly- aniline 1aniline 2 aniline 3 aniline 4 aniline 5 aniline 6 aniline 7 aniline 8Aniline 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 Dodecylbenzene sulfonic acid 4.24.2 4.2 4.2 4.2 — 4.2 4.2 Polyacrylic acid derivative 1.0 1.0 1.0 1.0 —1.0 1.0 1.0 4-methylaniline*1 0.03 0.03 — — 0.03 0.03 0.03 — Dodecanethiol*1 — — 0.05 — — — — — α-methylstyrene dimer*1 — — — 0.05 — — — —Tetrabutylammonium bromide*2 0.18 0.18 0.18 0.18 0.18 0.18 — — Yield (%)97 96 95 96 96 96 60 55 Dispersibility (wt %)*3 4.1 (1.3) 4.1 (1.3) 4.1(1.3) 4.1 (1.3) 3.4 (1.3) 2.0 (1.3) 2.7 (0.8) 2.7 (0.7) Dispersionstability*4 G G G G G G G P Conductivity (Scm⁻¹)*5 0.25 0.26 0.25 0.250.25 0.21 0.25 0.20 *1Molecular weight adjusting agent *2Phase transfercatalyst *3Shown by solid concentration (wt %) in polyaniline toluenedispersion (figures in parentheses in Table indicate polyaniline content(wt %)). *4Polyaniline toluene dispersion judged visually after standingat room temperature for 6 months. Formation of precipitate indicated by“P (poor)”, while non-formation indicated by “G (good)”. *5Pelletsproduced by compression molding machine measured by four-probe method.

As shown in Table I, it is clear that the Polyanilines 1 to 6 of thepresent invention are superior in yield and in dispersibility anddispersion stability with respect to toluene regardless of theconductivity being equal or greater than the Comparative Example ofPolyaniline 8. Note that it is clear that Polyaniline 7 is notnecessarily good in yield, but is superior in dispersion and dispersionstability with respect to toluene.

Examples 1 and 2 and Comparative Example 1

As shown in Table II, Polyaniline 1, 2 or 8 (0.05 g) and SBR (Nipol 1502made by Nippon Zeon) (1 g) were dissolved in 15 g of toluene, then thetoluene was distilled off in vacuo to obtain a polyaniline/SBRcomposite. The conductivity of the composite obtained is as shown inTable II.

TABLE II Formulation (parts by weight) Ex. 1 Ex. 2 Comp. Ex. 1 SBR 100100 100 Polyaniline 1 5 — — Polyaniline 2 — 5 — Polyaniline 3 0 — 5Conductivity (Scm⁻¹)*1 10⁻⁵ 10⁻⁴ 10⁻¹² *1Pressed in 15 × 15 × 0.2 cmmold at 100° C. for 10 minutes to prepare a rubber sheet which was thenmeasured for electroconductivity according to JIS K7194 method(conditions: room temperature, Mitsubishi Chemical Rorester GP).*

Standard Example 1, Examples 3 and Comparative Examples 2 to 4Fabrication of Dye-Sensitized Solar Cell Fabrication of Photoelectrode

A transparent conductive glass substrate (made by Nippon Sheet Glass,conducting layer made of fluorine-doped tin oxide, FTO, 10Ω/□) wascoated on its surface with a paste prepared by mixing titanium dioxidepowder (AEROXIDE TiO₂ P25, average particle size 25 nm, made by NIPPONAEROSIL), acetyl acetone, distilled water and a surfactant (Triton X100,made by Acros Organics) by a mortar, dried, then sintered at 460° C. for45 minutes, whereby a mesoporous titanium oxide thin film was formed onthe transparent conductive glass substrate. The glass substrate havingthis mesoporous titanium oxide thin film was dipped in an ethanolsolution (concentration of 3×10⁻⁴ mol/liter) of ruthenium complex dye(i.e., cis-di(thiocyanate)-N,N′-bis(2,2′-bipyridyl-4,4′-dicarboxylicacid) ruthenium (II) complex, Ruthenium 535, made by Solaronix) for 12hours. The result was washed by acetonitrile, then dried in a darklocation under a nitrogen flow to impregnate the mesoporous titaniumdioxide thin film with the sensitizing dye. This was used as aphotoelectrode.

Preparation of Electrolyte

Preparation of Liquid Electrolyte

Lithium iodide (0.5 mol/L), iodine (0.05 mol/L),1,2-dimethyl-3-propylimidazolium iodide (0.3 mol/L) and4-tert-butylpyridine (0.5 mol/L) were dissolved in3-methoxypropionitrile to use a liquid electrolyte.

Preparation of Ion Liquid Electrolyte 1

Lithium iodide (0.1 mol/L), iodine (0.15 mol/L) and 4-tert-butylpyridine(0.5 mol/L) were dissolved in 1-methyl-3-propylimidazolium iodide to usean ion liquid electrolyte 1.

Preparation of Ion Liquid Electrolyte 2

Lithium iodide (0.1 mol/L), iodine (0.15 mol/L),1-ethyl-3-methylimidazolium iodide and 4-tert-butylpyridine (0.5 mol/L)were dissolved in 1-ethyl-3-methylimidazoliumbis(trifluoromethylsulfonyl)imide to use an ion liquid electrolyte 2.

Standard Example 1

A transparent conductive glass substrate (made by Nippon Sheet Glass,conductive surface made of fluorine-doped tin oxide, FTO, 10Ω/□) wasformed on its surface with a platinum thin film, having a thickness of0.1 μm by spattering. This electrode was used as a counter electrode andwas layered with the above photoelectrode fixed with 2 clips. The liquidelectrolyte obtained above was introduced into the gap between theelectrodes to obtain a cell of Standard Example 1.

Standard Example 2

Except for using the ion liquid electrolyte 1 as the electrolyte, thecell of Standard Example 2 was fabricated in the same manner as inStandard Example 1.

Standard Example 3

Except for using the ion liquid electrolyte 2 as the electrolyte, thecell of Standard Example 3 was fabricated in the same manner as inStandard Example 1.

Example 1

A transparent conductive glass substrate (made by Nippon Sheet Glass,conductive surface made of a fluorine-doped tin oxide, 10Ω/□) was coatedon its surface with the polyaniline toluene dispersion 1, followed bydrying in vacuo to form polyaniline film. The thickness of thepolyaniline film was similar to that of the platinum film of StandardExample 1. Except for using this electrode as the counter electrode, thecell of Example 1 was fabricated in the same manner as in StandardExample 1.

Example 2

Except for using the ion liquid electrolyte 1 as the electrolyte, thecell of Example 2 was fabricated in the same manner as in Example 1.

Example 3

Except for using the ion liquid electrolyte 2 as the electrolyte, thecell of Example 2 was fabricated in the same manner as in Example 1.

Example 4

A transparent conductive glass substrate (made by Nippon Sheet Glass,conductive surface made of a fluorine-doped tin oxide, 10Ω/□) was coatedon its surface with the polyaniline toluene dispersion 4, followed bydrying in vacuo to form polyaniline film. The thickness of thepolyaniline film was similar to that of the platinum film of StandardExample 1. Except for using this electrode as the counter electrode, thecell of Example 4 was fabricated in the same manner as in StandardExample 1.

Example 5

Except for using the ion liquid electrolyte 1 as the electrolyte, thecell of Example 5 was fabricated in the same manner as in Example 4.

Example 6

Except for using the ion liquid electrolyte 2 as the electrolyte, thecell of Example 6 was fabricated in the same manner as in Example 4.

Comparative Example 1

An electrochemical polymerization of aniline was carried out in a 0.1mol/L aqueous hydrochloric acid solution containing 0.5 mol/L anilinedissolved therein at 0.5 mA for 2 hours using, a work electrode, atransparent conductive glass substrate (made by Nippon Sheet Glass,conductive surface made of a fluorine-doped tin oxide, 10Ω/□) and, as acounter electrode, a platinum electrode to form a polyaniline film on atransparent conductive glass substrate. The thickness of the polyanilinefilm was similar to that of the platinum film of Standard Example 1.Except for using this electrode as the counter electrode, the cell ofExample 4 was fabricated in the same manner as in Standard Example 1.

The thickness of the polyaniline film was similar to that of theplatinum film of Standard Example 1. Except for using this electrode asthe counter electrode, the cell of Example 4 was fabricated in the samemanner as in Standard Example 1.

Comparative Example 2

Except for using the ion liquid electrolyte 1 as the electrolyte, thecell of Comparative Example 2 was fabricated in the same manner as inComparative Example 1.

Comparative Example 3

Except for using the ion liquid electrolyte 2 as the electrolyte, thecell of Comparative Example 3 was fabricated in the same manner as inComparative Example 1.

Comparative Example 4

A transparent conductive glass substrate (made by Nippon Sheet Glass,conductive surface made of a fluorine-doped tin oxide, 10Ω/□) was coatedon its surface with the poly(3,4-ethylenedioxythiophene) waterdispersion (Baytron P made by Bayer,), followed by drying in vacuo toform poly(3,4-ethylenedioxythiophene) film. The thickness of thepoly(3,4-ethylenedioxythiophene) film was similar to that of theplatinum film of Standard Example 1. Except for using this electrode asthe counter electrode, the cell of Comparative Example 4 was fabricatedin the same manner as in Standard Example 1.

Comparative Example 5

Except for using the ion liquid electrolyte 1 as the electrolyte, thecell of Comparative Example 5 was fabricated in the same manner as inComparative Example 4.

Comparative Example 6

Except for using the ion liquid electrolyte 2 as the electrolyte, thecell of Comparative Example 6 was fabricated in the same manner as inComparative Example 4.

Comparative Example 7

A transparent conductive glass substrate (made by Nippon Sheet Glass,conductive surface made of a fluorine-doped tin oxide, 10Ω/□) was coatedon its surface with the poly(anilinesulfonic acid) water dispersion(Aquasave made by Mitsubishi Rayon), followed by drying in vacuo to formAldrich film. The thickness of the Aldrich film was similar to that ofthe platinum film of Standard Example 1. Except for using this electrodeas the counter electrode, the cell of Comparative Example 7 wasfabricated in the same manner as in Standard Example 1.

Comparative Example 8

Except for using the ion liquid electrolyte 1 as the electrolyte, thecell of Comparative Example 8 was fabricated in the same manner as inComparative Example 7.

Comparative Example 9

Except for using the ion liquid electrolyte 2 as the electrolyte, thecell of Comparative Example 9 was fabricated in the same manner as inComparative Example 7.

Each test cell obtained above was irradiated with light from 500 W Xelamp through an AM1.5 solar simulation filter and thephotocurrent-photovoltage characteristics were measured with a digitalsource meter. The results are shown in Table III.

TABLE III Jsc (mA/cm²) Voc (mV) FF η (%) Standard Ex. 1 14.1 723 0.666.7 Standard Ex. 2 7.8 681 0.62 3.3 Standard Ex. 3 10.1 632 0.61 3.9Example 1 14.0 724 0.65 6.6 Example 2 7.9 685 0.63 3.4 Example 3 10.1636 0.63 4.0 Example 4 14.2 722 0.65 6.7 Example 5 8.0 683 0.63 3.4Example 6 10.2 635 0.62 4.0 Comp. Ex. 1 9.4 681 0.62 4.0 Comp. Ex. 2 5.8635 0.58 2.1 Comp. Ex. 3 6.7 596 0.61 2.4 Comp. Ex. 4 11.8 686 0.61 4.9Comp. Ex. 5 6.2 645 0.57 2.3 Comp. Ex. 6 7.6 612 0.58 2.7 Comp. Ex. 74.7 581 0.58 1.9 Comp. Ex. 8 3.7 535 0.56 1.1 Comp. Ex. 9 4.8 524 0.571.4 Jsc: Short-circuit photocurrent Voc: Open-circuit photovoltage FF:Fill factor η: Energy conversion efficency

As is clear from the results shown in Table III, the cell according toExamples 1 and 4 of the present invention exhibited the values of Jsc,Voc and η, under light irradiation, similar to the cell of StandardExample 1 using a platinum film as a counter electrode, whereas thecells of Comparative Examples 1, 4 and 7 using other conductive polymerthin films as counter electrodes have small values of Jsc, Voc and η.

As is clear from the results shown in Table III, the cell according toExamples 2 and 5 of the present invention exhibited the values of Jsc,Voc and η, under light irradiation, similar to the cell of StandardExample 2 using a platinum film as counter electrode, whereas the cellsof Comparative Examples 2, 5 and 8 using other conductive polymer thinfilms as counter electrodes have small values of Jsc, Voc and η.

As is clear from the results shown in Table III, the cell according toExamples 3 and 6 of the present invention exhibited the values of Jsc,Voc and η, under light irradiation, similar to the cell of StandardExample 3 using a platinum film as counter electrode, whereas the cellsof Comparative Examples 3, 6 and 9 using other conductive polymer thinfilms as counter electrodes have small values of Jsc, Voc and η.

As explained above, according to the present invention, it is possibleto obtain a conductive polyaniline stably dispersed in an organicsolvent at a high yield. This conductive polyaniline is stably dispersedin an organic solvent, and therefore, can easily form a conductive filmor thin film by being coated or dried on a base material. The conductivefilm or thin film thus obtained is suitable for use for an antistaticmaterial, a transparent conductive film, etc. Further, by mixing with aconventional polymer material, it may be converted to a conductivematerial. Further, when the conductive polyaniline dispersion stable inan organic solvent is used, a counter electrode having propertiessimilar to, or greater than, those of conventional platinum thin layeron a substrate can be obtained at a lower cost and, therefore, can beadvantageously used in, for example, a dye-sensitized solar cell.

1. A photovoltaic device comprising (i) a photoelectrode composed of atransparent conducting layer and a metal oxide semiconductor mesoporousfilm, (ii) a counter electrode located opposite to the photoelectrodeand (iii) an electrolyte layer containing a redox couple present betweenthe both electrodes, said counter electrode being formed by a conductivesubstrate comprising, coated thereon, (A) polyaniline derived frompolymerization of aniline or aniline derivative, (B) sulfonic acidand/or (C) an organic polymer having a protonic acid group, (D) amolecular weight adjusting agent and (E) an organic solvent capable ofdissolving the sulfonic acid (B), the organic polymer having a protonicacid group (C) and the molecular weight adjusting agent (D).
 2. Adye-sensitized solar cell comprising a metal oxide semiconductormesoporous film of the photoelectrode of claim 1 and a photosensitizingdye carried thereon.